Entertaining a woman all night in an undergraduate's room is no more legal or illegal than entertaining her half the night.

This new, surprise legal argument, presented last night to the Committee on Houses, moved discussion of parietals from old quibbles over Massachusetts morals laws to the question of how students might react if visiting hour restrictions are lifted at Harvard Houses.

If the argument convinces the committee to recommend changing rules in upperclass Houses, Harvard would become the second Ivy League university--Columbia was first--to abolish visiting hour restrictions.

Emerging from a two-hour meeting with the Committee, representatives of the Harvard Undergraduate Council (HUC) expressed confidence that they have "settled" legal justifications previously used by the University for retaining parietal hours.

The morals laws which University lawyers had cited to support hours restrictions prohibit the operator of a "lodging house" from "knowingly" permitting a woman to be there "for the purpose of unlawfully having sexual intercourse."

A legal opinion obtained by HUC said allowing a woman in a house overnight instead of only until 1 a.m., under the present rule, would not constitute "knowingly" permitting intercourse.

Armed with the new legal interpretation, HUC urged the committee to recommend that the faculty:

* Eliminate visiting hours for women as long as they are "properly escorted into and out of the house."

* Permit women in freshman dormitories during times prescribed by the dean of freshmen.

* Permit women in club houses and other buildings under the jurisdiction of the dean of students only with his consent.

* Do away with the signout book because "the system punishes the naive and the honest."

* Decentralize dissemination of information about students by sending reports, such as police memoranda, to tutors rather than to the dean, and by permitting tutors to make more decisions.

The Committee is expected to consult university attorneys on the Hill & Barlow interpretation and, after deliberation, make its own recommendation to the faculty. The faculty, which has the final say, usually follows committee recommendations.

Suggestions to eliminate parietals have been made many times before. The university agreed last year to extend visiting hours but not do away with them. The latest efforts, however, are believed to carry more weight because the changes were suggested by a House Master and because of the new legal interpretation.

Master Bruce Chalmers of Winthrop House, who made the suggestion, said parietals "are no longer a controversial or emotional issue. The drastic change was made a year ago." Other supporters of the move implied that the University would not be making a drastic or revolutionary move by eliminating visitation restrictions which, they claim, are not being enforced anyway.