H. James Harrington answers (1):

This is not an unusual question. I have had it asked of me often. So after many failures and a few successes, I have narrowed down the options to three:

Approach 1: The Passive Approach
One option you have is to take no action and live with the offensive individuals. After all, this condition lasts for only one or two hours per week out of the 168 hours you have available. That's about one percent of your time and you probably won't be on this team for more than two or three years. (Not the preferred approach)

Approach 2: The Aggressive Approach
This is a very effective approach and usually gets immediate results. All you need is to hire Mike Tyson and have him nibble on the ears of the offenders, letting them know that if the condition occurs again, he will be back to take more aggressive action. But if you don't have the $3,000,000 to hire Mike Tyson, or if Mike is not available, you will need to consider approach #3. (The preferred approach)

Approach 3: The Integrated Team Approach
Your question concludes with the sentence, "What should I do?" Perhaps in that expression lies part of the problem; and, happily, a hint at a solution.  The more proper question is, "What should we do?"

You are to be commended for your individual efforts (which might be termed leadership, facilitation, or meddling, depending on how you approach them) in exercising initiative to improve the situation. But you have discovered that your independent efforts did not produce the desired results. As you have suggested in your observation that "their behavior often makes it difficult for the team to function," it has become a team issue, not solely a personal one. Here then, are suggestions for what the team, which includes you, might do. They are presented as an integrated and progressive approach:

Laying the Foundation:
Successful teams and effective teamwork are predicated on a clear and agreed-upon team charter. If you have one, review it and work to regain commitment to it. If you do not have one, the team should create it. It should contain:

• Team mission, vision and goal/objective statements, agreements on desired conduct - the ways in which team members will work together
• A process for reviewing progress toward goals and conformance to agreed-upon conduct, together with a feedback mechanism

Developing a Plan:
The team needs an agreed-upon approach to accomplishing its mission, reaching its objectives, and working together. That approach and plan should include:

• A definition of the current state and desired future state and identification of the gaps between the two, (this can and should include behavioral gaps)
• Identification of actual or potential barriers to achievement of the desired future state, (undesirable behavior can be identified without having to publicly castigate the 'troublemakers' at this stage)
• Strategies and action steps for narrowing the gaps, (the behavioral issues now become part of a broader context for meeting team objectives)
• Clear definition of roles, responsibilities and timelines, (a foundation for measurement and follow-up)
• Identification of competencies and behaviors necessary for success of the team

Managing Performance and the Consequences of Inappropriate Behavior
Depending on the maturity of your team and the extent of autonomy the organization intends for it, the following approaches to managing individual and team performance and the consequences of unsatisfactory performance may be the responsibility of the team itself. This can be delegated to certain members, or it may be the role of the facilitator, coach and/or leader. However accomplished, and by whom, the management of performance and its consequences, is as your own experience with the 'troublemakers' suggest, crucial to the success of the team. Some suggestions are:

• Do not focus just on the 'troublemakers;' the same principles and guidelines apply to every member of the team
• Focus on behavior and measurable results, do not get caught in the quagmire of attempting to evaluate or change attitudes; they will change only with time, if at all 
• Use the problem solving methods I hope your team has learned; in this case, don't treat symptoms, look for the root causes of the undesirable behavior
• Keep in mind that resistance to change is natural and to be expected; however, it must be managed. Understand when resistance is a function of ability versus willingness 
• Respond to ability issues through education and training
• Willingness issues are another matter, and must be addressed through prompt feedback, clear communication, and when necessary, consequence management. Appropriate behavior must make a difference - to the individual, as it does to the team
• Corrective action in the form of coaching when necessary, and,
• If the above approach does not achieve the needed results, the team or its leader, will have to be ready to help the 'troublemakers', should they remain such, find another job more in keeping with their individual talents and less demanding of team skills