US Anti-boycott Laws Prohibit Boycott of Israel

What do the Laws Prohibit?

Conduct that may be penalized under the TRA and/or prohibited under the EAR includes:

• Agreements to refuse or actual refusal to do business with or in Israel or with blacklisted companies.
  
• Agreements to discriminate or actual discrimination against other persons based on race, religion, sex, national origin or nationality.
  
• Agreements to furnish or actual furnishing of information about business relationships with or in Israel or with blacklisted companies.
  
• Agreements to furnish or actual furnishing of information about the race, religion, sex, or national origin of another person.

Implementing letters of credit containing prohibited boycott terms or conditions.

The TRA does not "prohibit" conduct, but denies tax benefits ("penalizes") for certain types of boycott-related agreements.

http://www.bis.doc.gov/complianceandenforcement/antiboycottcompliance.htm