The Graduate Employees and Students Organization delivered a letter to Yale President Richard Levin Thursday outlining specific instances of faculty behavior that they believe violate federal labor law.

The letter, which GESO also sent to Yale Provost Alison Richard, Graduate School Dean Susan Hockfield, and the fellows of the Yale Corporation, asked Levin’s administration to issue a public statement condemning the actions of faculty who have allegedly threatened free speech and assuring graduate students of their rights to organize.

In the letter, GESO said that if Levin fails to do so, the organization will file charges with the National Labor Relations Board next week.

Thursday’s letter is the latest in a series of correspondences between GESO and Levin. GESO chairwoman Anita Seth GRD ’05 said the letter responded to an Oct. 14 letter from Levin urging the group to bring forth to the dean or the provost any cases in which a graduate student felt that he or she had been subjected to improper behavior by a faculty member.

Seth said the group sent the letter because “tensions are heating up on campus” in many ways.

“The cumulative impact of the incidents over time has gotten to a crisis point,” she said.

Seth said she believes the cases of “harassment” of graduate students by faculty members contradicts the University’s policy on free speech.

“President Levin has said it’s very important for us to have a robust debate on campus,” she said. She said she does not think Levin has laid down guidelines pushing faculty members to promote freedom of expression.

Levin said that he had not had a chance to look at the letter.

GESO has been trying to organize graduate teaching and research assistants for over a decade but has not requested a formal election. University administrators have opposed unionization, maintaining that graduate students are not employees.

Thursday’s letter listed three cases in which faculty members allegedly threatened graduate students for engaging in conversations about union issues.

In one alleged incident, GESO accused professor Mark Mooseker of censoring discussion about unionization in his lab.

Kristie Starr GRD ’03 said that on Nov. 8, she and another GESO member were walking to Mooseker’s lab to talk to another GESO member. She said that Mooseker told the graduate students, who were wearing GESO pins, that they could not talk about union business in his lab.

Starr said she does not believe that GESO members should be limited as to when and where they can discuss unionization.

“I just want to be clear that graduate students should be able to talk to each other,” she said.

Mooseker was unavailable for comment.

The letter also detailed an alleged incident in which a professor threatened to throw any student out who participated in a strike. GESO members also alleged that another professor “expelled” graduates from his laboratory while talking about a union.

The letter said that GESO was “committed to doing everything possible to avoid unnecessary conflict and disruption on the campus.”

Seth said organization members might be forced to take actions if the University does not address the issues GESO has raised.

“It seems like that’s the way this campus is heading if there’s no action from the administration,” she said.

GESO leaders said in September that its members might strike this fall if the University did not hold discussions with them. The group has not held any actions. Last fall, University leaders developed a contingency plan in case of strikes or other job actions but have declined to comment on specific plans.