WHAT ARE THE CHANCES of receiving a rash of parking tickets next year, even though your car is legally parked - and then discovering that no one in the District government knows what to do about it? Very good, according to City Councilman David A. Clarke. That's why he has blocked Mayor Washington's proposal to change the way parking and other traffic violations are handled. True, the mayor's plan would probably bring in about $14 million to the city next year. The idea is to switch the enforcement of a large number of traffic laws from the police department to a government employee "citizen corps," and Mr. Clarke, who is chairman of the council's judiciary committee, has no objection to that. What troubles him is the absence of a D.C. municipal code setting forth the rules and regulations that determine how all the city's laws must be enforced.

For lack of such a code, District rules and regulations are scattered throughout a number of different documents and tucked away in a variety of government files. Some of the rules date back to 1840 and are obsolete, while others conflict with more recent legislation. For that reason, Mr. Clarke's isn't willing to authorize a group of citizens to do such things as suspend drivers' licenses, impose fines or mete out penalties until there is an accurate, comprehensive and readily available catalogue of what is or isn't a violation.

You may wonder why the city still doesn't have a municipal code. After all, in 1975 the City Council passed a law requiring Mayor Washington to produce one during 1976. Instead, the mayor produced a request for an extension of the deadline until 1977 - with a promise that he job would be done by then for sure. Since then, there have been only further excuses by the mayor and additional deadline extensions by the council. So far, there have been nine "emergency resolutions," giving the mayor more time to come up with the code. And in the next few days, council members will have to pass the 10th such resolution to keep those uncodified rules and regulations in effect.

The other day, Mayor Washington took his first step toward putting the code together. He issued an executive order calling for each agency to begin collecting all rules and regulations. It will probably be several months before the job is done, and even then the council will have only a listing of what exists - not a complete, up-to-date document. Meanwhile, spokesmen for the mayor contend there really is no connection between the code and the suggested revisions of the traffic laws. They also argue that the result of Mr. Clarke's action will be an unbalanced budge next year, since he is holding hostage $14 million that city officials had counted on. For his part, Mr. Clarke says the entire code doesn't have to be prodced before he releases the hold on those proposals. But he does want the mayor and other officials to get on immediately with doing the actual work - not just the procedure. Then he will approve changing traffic-law enforcement. We think that's a reasonable position for him to take.