33 CFR §20.1201

1. (a)This subpart applies whenever the Coast Guard suspends a mariner's credential without a hearing under 46 U.S.C. 7702(d).
2. (b)The Coast Guard may, for 45 days or less, suspend and seize a merchant mariner credential, license, certificate, or document if, when acting under the authority of the license, certificate, or document,—
   1. (1)A mariner performs a safety-sensitive function on a vessel; and
   2. (2)There is probable cause to believe that he or she—
      1. (i)Has performed the safety-sensitive function in violation of law or Federal regulation regarding use of alcohol or a dangerous drug;
      2. (ii)Has been convicted of an offense that would prevent the issuance or renewal of the merchant mariner credential, license, certificate, or document; or,
      3. (iii)Three years or less before the start of an S&R proceeding, has been convicted of an offense described in subparagraph 205(a)(3)(A) or (B) of the National Driver Register Act of 1982 (23 U.S.C. 401, note).