Conversely the courts can declare any law made as subsidiary legislation to be invalid or unacceptable under the ultra vires doctrine. Thus the law may be declared either procedurally or substantively ultra vires.
(a) Substantive Ultra Vires
However a law may be declared substantively ultra vires whether as the maker had no powers to make it. So now this may occur in a number of ways. As like a case, the Minister or Authority may have:as;
(i) exceeded the powers given through the Act;
(ii) exercised the power for another purpose rather than the particular rationale to that it was given, or
(i) Is acted unreasonably there in the sense explained through Greene, M.R. in Associated Provincial Picture Houses Ltd v Wednesbury Corporation
(b) Procedural Ultra Vires
Further a law will be declared procedurally ultra vires where the mandatory procedures prescribed in the enabling Act to its enactment are not tracks same like failure to publish it in the Gazette. So now look at a case of Mwangi V.R. in that Mwangi and another person were prosecuted and convicted with the Special Magistrate's Court, to charging one shilling instead of fifty cents to a haircut, Nairobi, contrary to Price Controller's Order No.20 of 1948 that should be made pursuant to Regulation 11(1) of the Defence as Control of Prices Regulations, 1945.
Now therefore further on appeal the convictions were set aside when the court's attention was drawn to the fact that the Order had not been published in the Gazette as should have been done. Since the order was now void and nobody could be charged for allegedly violating its provisions.