29 U.S.C. § 1141: Coercive interference

It shall be unlawful for any person through the use of fraud, force, violence, or threat of the use of force or violence, to restrain, coerce, intimidate, or attempt to restrain, coerce, or intimidate any participant or beneficiary for the purpose of interfering with or preventing the exercise of any right to which he is or may become entitled under the plan, this subchapter, section 1201 of this title, or the Welfare and Pension Plans Disclosure Act [29 U.S.C. 301 et seq.]. Any person who willfully violates this section shall be fined $100,000 or imprisoned for not more than 10 years, or both.