Students and faculty members protesting the appointment of a new dean, threw up a picket line and virtually closed the Catholic University Law School yesterday.

Only one of 27 classes scheduled for the school was convened, according to school officials. In that class, four students out of 60 showed up. About a half dozen other classes convened in makeshift quarters elsewhere on campus or in faculty member's law offices downtown.

Pickets and some students and professors are protesting the appointment of Dr. John Garvey as dean of the law school.

University president Clarence C. Walton named Dr. Garvey dean on Tuesday, with the appointment effective July 1. Protesters have been demanding that the appointment be rescinded and Garvey's name be submitted to a joint student-faculty-alumni screening committee formed to recommend a dean. Garvey, a member of the law school faculty for 26 years, was appointed outright and did not go through the screening committee.

The selection of a new dean for the law school has embroiled students and faculty in discussion and deliberation since dean E. Clinton Bamberger, Jr. resigned and returned to government service in October 1975.

The university administration then appointed the 12-member screening committee to recommend a successor. One of those recommended, John E. Murray, Jr., became the subject of intense controversy over his intentions for the school's legal services clinic and removed himself from consideration.

Walton, in naming Dr. Garvey to the post, noted that the school had had a succession of acting deans, and he feared more debate and delay over further search committee recommendations. The committee last month recommended another law school professor, Lawrence Velvel.

A group of students marched to the president's office on Wednesday and demanded that Dr. Garvey's name be withdrawn and submitted to the search committee, Walton refused.

Some 350 of the school's 700 students have signed a petition protesting Walton's decision.