In doing some research for one of our Locals on management's right to assign work, I found this nice bit of info in the DC Circuit Court decision where they overturned the FLRA and arbitrator's rulings over the Mission Critical Roster. While the decision was technically a 'loss' for the Union, there's still good stuff in it that we can benefit from.
Section 7106(a) gives an agency an exclusive, non-negotiable right to assign work but, under § 7106(b), it may bargain with the representative of its employees over the “procedures” it will use when it exercises that authority and the “appropriate arrangements” it will make for any employee “adversely affected” by a particular action. An agreement prescribing such “arrangements” and “procedures,” that is, the “impact and implementation” of an agency’s management right, therefore covers the content of the agency’s decisions made under that rubric. See Dep’t of Navy, 962 F.2d at 50 (“Although an agency is not required to bargain with respect to its management rights per se, it is required to bargain about the impact and implementation of those rights”). Article 18, specifically in sections (d) and (g), reflects the parties’ earlier bargaining over the impact and implementation of the Bureau’s statutory right to assign work. See § 7106(b) (permitting bargaining over the “numbers, types, ... or positions assigned to any ... work project or tour of duty”). Specifically, these provisions represent the agreement of the parties about the procedures by which a warden formulates a roster, assigns officers to posts, and designates officers for the relief shift.
So, to break it down, when the Agency negotiated Article 18, they locked in what the “procedures” [§ 7106(b)(2)] and “appropriate arrangements” [§ 7106(b)(3)] would be in terns of them exercising their rights under § 7106(a). That said, management can't arbitrarily deviate from Article 18, just by saying, "management's right to assign work"; the language that they agreed to in the contract binds them into 'how' they will exercise that right... they're stuck with it.