An act of Congress which prescribed as a qualification for practice before the federal courts an oath that the attorney had not participated in the Rebellion was found unconstitutional since it operated as a punishment for past acts.[1477] But a statute which denied to polygamists the right to vote in a territorial election, was upheld even as applied to a person who had not practiced polygamy since the act was passed, because the law did not operate as an additional penalty for the offense of polygamy but merely defined it as a disqualification of a voter.[1478] A deportation law authorizing the Secretary of Labor to expel aliens for criminal acts committed before its passage is not _ex post facto_ since deportation is not a punishment.[1479] Likewise an act permitting the cancellation of naturalization certificates obtained by fraud prior to the passage of the law was held not to impose a punishment but simply to deprive the alien of his ill-gotten privileges.[1480] Change in Place or Mode of Trial A change of the place of trial of an alleged offense after its commission, is not an _ex post facto_ law. If no place of trial was provided when the offense was committed, Congress may designate the place of trial thereafter.[1481] A law which alters the rule of evidence to permit a person to be convicted upon less or different evidence than was required when the offense was committed is invalid,[1482] but a statute which simply enlarges the class of persons who may be competent to testify in criminal cases is not _ex post facto_ as applied to a prosecution for a crime committed prior to its passage.[1483] Clause 4. No Capitation, or other direct, Tax shall be laid, unless in Proportion to the Census or Enumeration herein before directed to be taken. DIRECT TAXES The Hylton Case