I don't know at what time of day on 1-Dec-2016 the new rules were issued (in which timezone)
And, as you probably know already, the rules do not have a statement such as "These new rules take effect from hh:mm UTC on dd-mmm-yyyy)

However, if it important to you to be able to fly more than one UK-ME/etc flight, then I think you have a reasonable argument that you should be allowed to - can the airline prove what time of day (in which timezone) your tickets were purchased? And how that time compares to the time at which the new rules issued?