NEW YORK (CNN/Money) - A key fact has been lost amid all of the fiery rhetoric and political posturing surrounding new federal overtime rules that took effect Monday: Some 18 states have overtime regulations that effectively nullify federal rules.

Under the Fair Labor Standards Act, state employment laws that are more generous to workers than federal statutes are the ones that employers must follow.

"That's the real story," said Jonathan Sulds, a New York lawyer who practices employment law with Akin Gump Strauss Hauer & Feld, a national law firm. "Sometimes states have regulatory schemes that are more protective than the federal scheme."

Most states have what are called "me too" laws, meaning the state's overtime rules automatically follow federal law.

But according to Allison Blakley, a Chicago employment lawyer at Sonnenschein Nath & Rosenthal, 18 states have taken advantage of their right to set up their own overtime rules. They now have to decide whether to update their regulations to conform with the new federal guidelines, stick to the old rules or have separate schemes altogether.

The outliers are Alaska, Arkansas, California, Colorado, Connecticut, Hawaii, Illinois, Kentucky, Maryland, Minnesota, Montana, New Jersey, North Dakota, Oregon, Pennsylvania, Washington, West Virginia, and Wisconsin.

Overtime has always been a political hot potato, with labor groups generally opposed to rule changes and business groups eager to restrict time-and-a-half provisions. This being an election year, it's far from a given that the 18 state legislatures will simply adopt the federal government's revamp.

One state in open rebellion is Illinois.

Illinois used to be "me too" state. But this spring, as battles waged in Congress over the Bush Administration's proposed overtime revisions, Illinois governor Rod Blagojevich signed into law an overtime bill that rejected most of the federal changes.

State legislators did, however, raise the salary level -- from $155 a week, or $8,060 a year, to $425 a week, or $22,100 a year -- above which an employee could be considered ineligible for overtime pay. That's below the new federal level of $455 a week, or $23,660.

Another state that's unlikely to follow the federal government's lead is California, where 14.5 million non-farm workers are protected by workplace rules that are among the most employee-friendly in the country.

For example, millions of clock-punchers earn overtime if they work more than 8 hours in a single day and are entitled to double their hourly rate for workdays that exceed 12 hours. The overtime kicks in even if the worker logs only a standard 40-hour week.

Under federal law, however, eligible employees start earning overtime only when the 40-hour mark is passed.

California workers also have an easier time meeting the state's time-and-half qualifications, according to Kirby Wilcox, a San Francisco employment lawyer.

For instance, California's salary threshold for overtime ineligibiilty is $28,080 a year, $4,420 more than the federal level,

Under federal law, a computer engineer earning an hourly rate of $27.63 could be disqualified from overtime. In California, the country's high-technology center, the minimum is $44.63.

In addition, California employers looking to deny a worker overtime pay have a harder time meeting the so-called "duties" test, which is one of three hurdles that an employer has to clear under federal law to classify a worker as ineligible for time-and-a-half.

"For every exemption you can think of, California requires everything that's in the federal rules plus something more," said Wilcox, a partner with Paul, Hastings, Janofsky & Walker.

Many states, even those that basically follow federal overtime law, carve out quirky exceptions. Often these anomalies deal with jobs in a key industry.

Here are a few examples from the CCH Business Owner's Toolkit TM, a guide for employers published by CCH Incorporated:

• In Montana, employees at "county elevators," "houseparents," cooks, "camp tenders" and livestock handlers are ineligible under state law for overtime.
• In Colorado, ski lift operators and on-mountain food service workers don't get overtime for 40-hour workweeks but do earn time-and-a-half for more than 12-hours or work in a day.
• The District of Columbia singles out "casual" babysitters as ineligible for overtime.
• In Kansas, state prisoners are out of luck too.
• Doesn't matter if you are a lifeguard or a hula dancer, there's no overtime if you work in Hawaii and make at least $2,000 per month.
• Most in Missouri are eligible for working past 40 hours in a week. But amusement park workers first have to log 52 hours.

The disparities between state and federal overtime laws drive many employers, especially national food and retail chains with workers around the country, crazy. Mistakes, intentional or not, have proven costly as court battles between employees and their bosses over pay have become increasingly common.

One of the main goals of the revised federal rules is to reduce the number of overtime lawsuits. In the short-term, as states grapple with whether to adopt the federal changes or stick to their own scheme, there's bound to be more confusion, not less.

"Nobody understands this law," said Jeffrey Pollack, a New York employment lawyer who operates www.OverTimeLawyer.net, a web site for workers.