You don't need server side, it can be done client side.
function arrestGui()
local arrest = getElementData(localPlayer, "arrest")
if arrest then
outputChatBox("arrest: "..arrest)
guiSetVisible(windowArrest, true)
showCursor(true)
guiSetText(GUIEditor_Label[2], "arrests: "..arrest)
else
outputChatBox("you don't have any arrest")
end
end
addCommandHandler("arrest", arrestGui)