This memo provides department wide guidance to ICE, CBP, and USCIS to clarify current DHS enforcement priorities. It discusses the background of prosecutorial discretion in immigration law and sets out the following civil immigration enforcement priorities: priority 1, threats to national security, border security, and public safety; priority 2, misdemeanants and new immigration violators; priority 3, other immigration violations (including those with a final order of removal except when they qualify for asylum or another form of immigration relief). This memo also discusses detention priorities and identifies those suffering from serious physical or mental illness, who are disabled, elderly, pregnant, or nursing, who demonstrate that they are primary caretakers of children or an infirm person, or whose detention is otherwise not in the public interest, as a low priority for detention.