Charles S. (Chuck) Robb, son-in-law of the late President Lyndon B. Johnson, meets the Virginia constitutional requirements to run for lieutenant governor despite a 10-month lapse in his qualification to vote, according to an opinion by state Democratic Party counsel Charles R. Hofheimer.

Hofheimer, of Virginia Beach, stated his opinion in a letter Wednesday to state party chairman Joseph T. Fitzpatrick, who must certify Democratic candidates for statewide office by April 20, Fitzpatrick, of Norfolk, could not be reached for comment, but is expected to follow Hofheimer's opinion.

Fitzpatrick asked for the legal opinion after state Sen. Joseph V. Gartlan (D-Fairfax) raised the issue of Robb's qualifications in a recent Senate Democratic caucus. Gartlan said any doubts about Robb's standing should be put to rest quickly to prevent a Republican challenge if Robb wins the June 14 Democratic primary.

The question of Robb's qualifications to run arises from a state constitutional provision requiring lieutenant governors to have been registered voters for five years preceding their election. Candidates in this year's election must have been registered continously since Nov. 9, 1972.

For more than 10 months after that date, Robb was listed on Arlington County voter registration rolls but was not eligible to cast a vote there because he did not have a place to live in the county. He sold his Arlington home on Sept. 2, 1972, and was not agin eligible to vote until he registered in Richmond on Sept. 28, 1973.

Hofheimer said in an interview that his opinion that Robb is qualified to run is based primarily on the legal conclusion that a person need not be eligible to cast a ballot to be a "registered voter."

Hofheimer said he supports the view of Robb's campaign counsel, Glenn R. Croshaw, also of Virginia Beach, that the "registered votes" requirement in the Constitution was adopted to provide "readily verifiable" proof that a candidate had lived in the state for five years.

In a memorandum to Hofheimer, Croshaw argued that looking beyond registration rolls to other qualifications to vote would introduce uncertainities in determining the eligibility of candidates. Crowshaw said that the registered voter requirement was added to the Virginia Constitution in 1970 to avoid disputes over residency.

Fitzpatrick must certify candidates to the state Board of Elections, whose three members must in turn rule them qualified before putting their names on the ballot.