A-01 / Legal boundary
Spend or promise money without the necessary fiscal authority
Purpose, amount, period-of-availability and apportionment limits constrain obligations and expenditures. A mission, strategy, NDAA authorization amount or official promise does not by itself supply available money.
Scope and exceptions
Congress can expressly provide contract authority, no-year funds, special accounts or other exceptions. Apply the actual statute; do not assume all future commitments are prohibited.
Planning implication
Pair every positive authority with a lawful account and funds-control chain.