This chapter points out the significant challenges in holding foundation model developers and deployers clearly responsible for the uses and outputs of their creations under US law. Scienter requirements, and difficulties in creating proof, make it challenging to establish liability under many statutes with civil penalties and torts. Constitutional protections for speech may shield model-generated outputs, or the models themselves, from some forms of regulation—though legal scholars are divided over the extent of these protections. And legal challenges to agencies’ authority over AI systems could hamstring regulators’ ability to proactively address foundation models’ risks. All is not lost, though. Each of these doctrines do have potential pathways to liability and recourse. However, in all cases there will likely be protracted battles over liability involving the issues described in this chapter.