California of course has such a law.  I

n the state of Washington, the law is very similar.  You must be presented
with a estimate which then becomes the contract for the work to be
performed.  Your signing of that estimate is the contract execution to have
the work done.  It can be interpreted that if there is no contract, the cost
of the labor to the consumer is zero, as he did not contract to have that
labor performed.  Parts of course are not covered and must be paid by the
consumer.

So if in WA you have work done on your car,  the registered shop neglected
to provide you with a written estimate which you signed before work began,
your obligation to pay for the labor part of the work is unsubstantiated
although the parts are your responsibility.

The shop cannot by law hold your car or file a lien for the labor as there
was no contract for the work done.

Interesting, but not unusual.  If you contract for work to be done on your
house, via a contractor, who provides you with an estimate which you sign,
you have an obligation to pay for that work when it meets the contractual
specification.

If the contractor fails to provide such a document...Q.E.D.

To find out the requirements for having a licensed shop work on your car,
you should peruse the state's DMV or similar web pages or contact your auto
club or the state consumer protection office.  Make a copy of the rules and
carry one in your car.  Shows the shop that you are a knowledgeable consumer
and concerned about your side of reputable business dealings.