This command controls whether or not the user may interactively resize a top-level window. If width and height are specified, they are boolean values that determine whether the width and height of window may be modified by the user. In this case the command returns an empty string. If width and height are omitted then the command returns a list with two 0/1 elements that indicate whether the width and height of window are currently resizable. By default, windows are resizable in both dimensions. If resizing is disabled, then the window's size will be the size from the most recent interactive resize or wm geometry command. If there has been no such operation then the window's natural size will be used.
wm resizable $win 0 0
seems to "inactivate" the "maximum" button with some (which?) window managers.