The Gov cannot force a company to suspend div or buy backs because that is from the profit side of the house. A company will however stop divs or buy backs for any reason they think may affect the companies finnancial health...example if it got to the point of deciding if LMT were to fund the pension plan or pay the quartely div because of money flow issues...guess what would get cut first?
Ref "can government pressure defense contractor to suspend div and buybacks"
Answer: yes, the government can pressure defense contractors in many ways for many things, but cannot compel them to do something that is not within the law.
One form of pressure could be the President of the United States using the Bully Pulpit to shame defense contractors, but the defense contractors are not legally bound by this type of pressure. The House of Representatives can also pressure companies by issuing subpoenas to appear in front of hearings to answer their questions, although this may very well be uncomfortable the companies are not forced into doing what members of the House imply.