Source: https://www.justice.gov/jm/criminal-resource-manual-1601-background-18-usc-351
Timestamp: 2019-04-26 12:28:14+00:00

Document:
Section 351 of Title 18, United States Code, makes it a Federal offense to kill or kidnap a Member of Congress, a Member-of-Congress elect, certain specified executive branch officials, a major Presidential or Vice Presidential candidate, a Justice of the Supreme Court or a person nominated to be a Justice. Attempts and conspiracies to commit such offenses or to assault any such individual are also made criminal by this section.
As of April 24, 1996, all Federal officials covered under 18 U.S.C § 351 are also covered under the expanded coverage provided in § 1114 of Title 18 for all employees of all branches, departments, and agencies of the United States Government, including active duty military personnel. See Antiterrorism and Effective Death Penalty Act of 1996, § 727(a), Pub. L. 104-132, 110 Stat. 1214, 1302. However, unlike § 351, section 1114 requires that the violent attack upon the Federal official be committed while the Federal official "is engaged in or on account of the performance of official duties." Hence, § 351 is a broader statute and should continue to be used for those Federal officials encompassed within its ambit. Section 1114 and related statutes are now available, however, for violent attacks upon other officials and employees of the Congress and the Supreme Court not covered by § 351.
It should also be noted that family members of all Federal employees are now protected by § 115(a)(1) of Title 18 against assault, kidnapping, and murder, as well as attempts or threats to assault, kidnap, or murder. However, such violent acts must be done "with the intent to impede, intimidate, or interfere with" such Federal employee "while engaged in the performance of official duties, or with intent to retaliate against" such Federal employee.
Section 115(a)(2) of Title 18 covers threats against all Federal employees, including those covered by § 351, when such threat is done "with intent to impede, intimidate, or interfere with" such Federal employee "while engaged in the performance of official duties, or with intent to retaliate against" such Federal employee.
In addition, § 115(a)(2) of Title 18 was expanded, as of April 24, 1996, to cover assault, kidnapping, and murder, as well as attempts to kidnap or murder or threats to assault, kidnap, or murder, any former Federal employee, including any former Member or employee of Congress or former Justice or employee of the Supreme Court, with intent to retaliate against such person on account of the performance of official duties. See Antiterrorism and Effective Death Penalty Act of 1996, § 727(b), Pub. L. 104-132, 110 Stat. 1214, 1302. Moreover, the family members of all former Federal employees are now covered under § 115(b) against assault or murder, including any attempt to assault or murder, directed towards them on or after April 24, 1996, provided such act was done with intent to retaliate against the former Federal employee on account of the performance of his/her official duties during the term of his/her Federal service.

References: § 351
 § 1114
 § 727
 § 351
 § 351
 § 351
 § 115
 § 351
 § 115
 § 727
 § 115