38 CFR § 3.301 - Line of duty and misconduct.
(a) Line of duty. Direct service connection may be granted only when a disability or cause of death was incurred or aggravated in line of duty, and not the result of the veteran's own willful misconduct or, for claims filed after October 31, 1990, the result of his or her abuse of alcohol or drugs.
(c) Specific applications; willful misconduct. For the purpose of determining entitlement to service-connected and nonservice-connected benefits the definitions in §§ 3.1 (m) and (n) of this part apply except as modified within paragraphs (c)(1) through (c)(3) of this section. The provisions of paragraphs (c)(2) and (c)(3) of this section are subject to the provisions of § 3.302 of this part where applicable.
(1) Venereal disease. The residuals of venereal disease are not to be considered the result of willful misconduct. Consideration of service connection for residuals of venereal disease as having been incurred in service requires that the initial infection must have occurred during active service. Increase in service of manifestations of venereal disease will usually be held due to natural progress unless the facts of record indicate the increase in manifestations was precipitated by trauma or by the conditions of the veteran's service, in which event service connection may be established by aggravation. Medical principles pertaining to the incubation period and its relation to the course of the disease; i.e., initial or acute manifestation, or period and course of secondary and late residuals manifested, will be considered when time of incurrence of venereal disease prior to or after entry into service is at issue. In the issue of service connection, whether the veteran complied with service regulations and directives for reporting the disease and undergoing treatment is immaterial after November 14, 1972, and the service department characterization of acquisition of the disease as willful misconduct or as not in line of duty will not govern.
(2) The simple drinking of alcoholic beverage is not of itself willful misconduct. The deliberate drinking of a known poisonous substance or under conditions which would raise a presumption to that effect will be considered willful misconduct. If, in the drinking of a beverage to enjoy its intoxicating effects, intoxication results proximately and immediately in disability or death, the disability or death will be considered the result of the person's willful misconduct. Organic diseases and disabilities which are a secondary result of the chronic use of alcohol as a beverage, whether out of compulsion or otherwise, will not be considered of willful misconduct origin. (See §§ 21.1043, 21.5041, and 21.7051 of this title regarding the disabling effects of chronic alcoholism for the purpose of extending delimiting periods under education or rehabilitation programs.)
(3) Drug usage. The isolated and infrequent use of drugs by itself will not be considered willful misconduct; however, the progressive and frequent use of drugs to the point of addiction will be considered willful misconduct. Where drugs are used to enjoy or experience their effects and the effects result proximately and immediately in disability or death, such disability or death will be considered the result of the person's willful misconduct. Organic diseases and disabilities which are a secondary result of the chronic use of drugs and infections coinciding with the injection of drugs will not be considered of willful misconduct origin. (See paragraph (d) of this section regarding service connection where disability or death is a result of abuse of drugs.) Where drugs are used for therapeutic purposes or where use of drugs or addiction thereto, results from a service-connected disability, it will not be considered of misconduct origin.
(d) Line of duty; abuse of alcohol or drugs. An injury or disease incurred during active military, naval, or air service shall not be deemed to have been incurred in line of duty if such injury or disease was a result of the abuse of alcohol or drugs by the person on whose service benefits are claimed. For the purpose of this paragraph, alcohol abuse means the use of alcoholic beverages over time, or such excessive use at any one time, sufficient to cause disability to or death of the user; drug abuse means the use of illegal drugs (including prescription drugs that are illegally or illicitly obtained), the intentional use of prescription or non-prescription drugs for a purpose other than the medically intended use, or the use of substances other than alcohol to enjoy their intoxicating effects.