31 USC 3713 - Priority of Government claims

(1) A claim of the United States Government shall be paid first when
(A) a person indebted to the Government is insolvent and
(i) the debtor without enough property to pay all debts makes a voluntary assignment of property;

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(ii) property of the debtor, if absent, is attached; or
(iii) an act of bankruptcy is committed; or
(B) the estate of a deceased debtor, in the custody of the executor or administrator, is not enough to pay all debts of the debtor.
(2) This subsection does not apply to a case under title 11.
(b) A representative of a person or an estate (except a trustee acting under title 11) paying any part of a debt of the person or estate before paying a claim of the Government is liable to the extent of the payment for unpaid claims of the Government.