A processor of an aspect includes an instruction fetch unit to fetch a pair of instruction order enforcement instructions. The pair of instruction order enforcement instructions are part of an instruction set of the processor. The pair of instruction order enforcement instructions includes an activation instruction and an enforcement instruction. The activation instruction is to occur before the enforcement instruction in a program order. The processor also includes an instruction order enforcement module. The instruction order enforcement module, in response to the pair of the instruction order enforcement instructions, is to prevent instructions occurring after the enforcement instruction in the program order, from being processed prior to the activation instruction, in an out-of-order portion of the processor. Other processors are also disclosed, as are various methods, systems, and instructions.