Client.lua

local allowedToUse = false
Citizen.CreateThread(function()
    TriggerServerEvent("Roleplay-Menu.getIsAllowed")
end)

RegisterNetEvent("Roleplay-Menu.returnIsAllowed")
AddEventHandler("Roleplay-Menu.returnIsAllowed", function(isAllowed)
    allowedToUse = isAllowed
end)

-- In your resource, check "allowedToUse" whenever you want to "do" something that needs permissions, for example
if allowedToUse then
RegisterCommand('onduty', function()
    onduty = not onduty
		local str = nil
		if onduty then
			str = "^2 onduty"
		else
			str = "^1 offduty"
		end
	TriggerEvent('chatMessage', "^1[SYSTEM]:^0 You are now"..str.."^0.")
    else
        TriggerEvent("chatMessage", "", {255,255,255}, "^1You're Not Authorised To Use This Command!")
end