"SECTION 16. Assignment of Internal Revenue Officers Involved in Excise Tax Functions to Establishments Where Articles Subject to Excise Tax are Produced or Kept. - The Commissioner shall employ, assign, or reassign internal revenue officers involved in excise tax functions, as often as the exigencies of the revenue service may require, to establishments or places where articles subject to excise tax are produced or kept: Provided, That an internal revenue officer assigned to any such establishment shall in no case stay in his assignment for more than two (2) years, subject to rules and regulations to be prescribed by the Secretary of Finance, upon recommendation of the Commissioner.

"SECTION 17. Assignment of Internal Revenue Officers and Other Employees to Other Duties. - The Commissioner may, subject to the provisions of Section 16 and the laws on civil service, as well as the rules and regulations to be prescribed by the Secretary of Finance, upon the recommendation of the Commissioner, assign or reassign internal revenue officers and employees of the Bureau of Internal Revenue, without change in their official rank and salary, to other or special duties connected with the enforcement or administration of the revenue laws as the exigencies of the service may require: Provided, That internal revenue officers assigned to perform assessment or collection functions shall not remain in the same assignment for more than three (3) years: Provided, further, That assignment of internal revenue officers and employees of the Bureau to special duties shall not exceed one (1) year.

"SECTION 18. Reports of Violation of Laws. - When an internal revenue officer discovers evidence of a violation of this Code or of any law, rule or regulation administered by the Bureau of Internal Revenue, of such character as to warrant the institution of criminal proceedings, he shall immediately report the facts to the Commissioner, through his immediate superior, giving the name and address of the offender and the names of the witnesses, if possible: Provided, That in urgent cases, the Revenue Regional Director or Revenue District Officer, as the case may be, may send the report to the corresponding prosecuting officer. In the latter case, a copy of his report shall be sent to the Commissioner.